Can challenges be re-written to be a little clearer?
I (ML) think an overarching subsection early on, clarifying especially the data.frame-centric nature of dplyr and tidyverse (always DF in; always DF out) might be helpful in general and with the tricky assignment of the data.frame vs assignment to a column within a data.frame. Also, “here are five fundamental tasks you’ll learn to do in data.frames. Dplyr has one function for each of these tasks.”
Variance exercise: may need to reword parts to make more clear the goal of the exercise. "Can you make a plot that shows the distribution of country level gdp by without summarizing beforehand?"
Consider changing variance to mean. Variance might be one weight too many for some.
Graphic like PIPE graphic in SWC Unix materials
Typo in code chunk in pipe section
How prominent should the pipe be? Much disagreement about this. Also, how much should we make a point of nesting and repeated assigning vs. just demoing the "right" (piped) way to do things?
In addition to #29 and #30: